PDF is an inherently difficult format from the standpoint of people who are blind using a screen reader to listen the PDF read aloud. Similarly, people with low vision and people with cognitive impairments using text-to-speech technology may encounter difficulties with improperly tagged PDF documents.
While the process for creating accessible PDFs continues to develop, it is still far from intuitive or efficient. Instead, consider providing an accessible alternative in addition when distributing a PDF. For example, if you are emailing a colorful flier as a PDF attachment, include all the information from the flier in the body of the email. Let your readers know that all the information in the flier is contained in the email so they can be assured that they are getting all the important details. And of course, make sure the body of your email meets accessibility guidelines.
Find information about creating accessible email and other document types in the Technology Accessibility Toolkit.